OK OK boys... yes I know 2n2222's are wonderful and plentiful, but I
have a heap of geriatric bipolar power transistor I thought it might
be worth experimenting with:-

2n3055 (three)

2n3054 (four)

2n3739 (two)

2n4800 (one)

Sony D292 U38 (two)

Sony 2sc895 (one)

I thought if you can get anything up to 500mW with a general purpose
NPN, then what can you get out of an old power transistor?

I also have a load of BD139 medium-power transistors...?

Any thoughts?

In addition, I am still looking for the COMPONENT LAYOUT for the PCB
for a QRP
transmitter called "little joe" described in 9-81 in QST. I am not
looking for just the circuit diagram but where the parts GO on the
PCB!

Stephen G7VFY

07956-544202

The problem with power transistors is that they are big, and all other
things being equal, more size spells more capacitance, and mosr capacitance
spells more trouble at higher frequencies.

Chances are, you might do some good with some of them on 80, but you're not
likely to make them play nice on 20. If you notice, the 3055 has an Ft of
2.5 MHz, 3054 3 MHz. The 2N2222 has an Ft of 250 MHz, so you can see
there's a little difference there.

Your 3739 has a 10 MHz Ft, so you might get a little gain out of it on 80.
The 2SC895 I *think* is 20 (could only find a bad copy of the datasheet).
It will take a fair bit of tinkering to make parts like that work at all,
and they won't work well.

...

"mister35mm" wrote in message
oups.com...
OK OK boys... yes I know 2n2222's are wonderful and plentiful, but I
have a heap of geriatric bipolar power transistor I thought it might
be worth experimenting with:-

2n3055 (three)

2n3054 (four)

2n3739 (two)

2n4800 (one)

Sony D292 U38 (two)

Sony 2sc895 (one)

I thought if you can get anything up to 500mW with a general purpose
NPN, then what can you get out of an old power transistor?

I also have a load of BD139 medium-power transistors...?

Any thoughts?

In addition, I am still looking for the COMPONENT LAYOUT for the PCB
for a QRP
transmitter called "little joe" described in 9-81 in QST. I am not
looking for just the circuit diagram but where the parts GO on the
PCB!

Stephen G7VFY

07956-544202

On Sat, 3 Feb 2007 19:48:34 -0500, "xpyttl"
wrote:


Chances are, you might do some good with some of them on 80, but you're not
likely to make them play nice on 20. If you notice, the 3055 has an Ft of
2.5 MHz, 3054 3 MHz. The 2N2222 has an Ft of 250 MHz, so you can see
there's a little difference there.

Your 3739 has a 10 MHz Ft, so you might get a little gain out of it on 80.
The 2SC895 I *think* is 20 (could only find a bad copy of the datasheet).
It will take a fair bit of tinkering to make parts like that work at all,
and they won't work well.

The current gain drops to unity at fT, but you might still get some
voltage and power gain around such frequencies in a common base
configuration. This is the case in many microwave bipolar amplifiers,
since you can not get transistors (or would be too expensive) with fT
sufficiently high for common emitter configurations on a particular
band.

However, I have not seen common base amplifiers for HF, since RF power
transistors with sufficiently high fT are easily available for HF.

Paul OH3LWR

Ok then.... I give up.

I had checked out the maximum frequency on all these old bipolar power
trannies, and basically, I've stuck them on ebay.

I seem to have quite a few BD139 power transistors. They are not as
'meaty' looking as they are medium power, plastic cased and are not
small signal types.

Looking at the data sheet he- http://www.ortodoxism.ro/
datasheets2/6/0rwiehk82adehe25p4gkxjros2yy.pdf

It say these transistors are good up to 190MHz, so does this mean I
can use one instead of a 2n2222 (I have lots of these BD139's and if
they'll work, I'd like to try)

Would I have to change any of the component values of the Michigan
Mighty Mite ( http://cs.okanagan.bc.ca/ve7ouc/eng/kc6wdk-
mirror/transmitter.html ) component values to use a BD139? Say 1/2 or
1 watt resistors?

Stephen
G7VFY

On 2 Feb 2007 21:23:07 -0800, "mister35mm"
wrote:

OK OK boys... yes I know 2n2222's are wonderful and plentiful, but I
have a heap of geriatric bipolar power transistor I thought it might
be worth experimenting with:-

2n3055 (three)

2n3054 (four)

I used time ago with good success up to 100MHz & 1W
2n3053 ...


--
Regards , SPAJKY ®
mail addr. @ my site @ http://www.spajky.vze.com
4y - "Tualatin OC-ed / BX-Slot1 / inaudible setup!"